Tires available for commercial sale are generally one of two types: new tires and tires which have been retreaded. Because of the ever escalating cost of new tires, the retreading market has become more appealing to many consumers.
The retreading of used tires serves a significant economical function. Not only does it provide a less expensive product to the consuming public, but it also limits waste which results from the discarding of tire carcasses.
Prior to the conduct of retreading operations upon a used tire carcass, it is necessary to ascertain if any foreign objects are embedded in the tread portion of the tire or if any cracks, fissures, or holes exist therein. The prior art has typically relied upon visual inspection in order to make this determination. If such defects are found to exist, they are cured prior to continuing with retreading operations.
Visual inspection for such defects tends to be slow and time consuming. More importantly, however, this method of searching for defects is, at best, unreliable. With this method, a tire is rotated on a mounting stand, and an inspector visually observes the tread portion of successive tires as they pass beneath his gaze. Although a trained eye might detect defects which would not be apparent to the untrained observer, the monotony of observing the tread portions of successive tires make it difficult, after a period of observation, to reliably spot such defects.
Additionally, some defects are so minute that they escape the detection of even a trained, experienced observer. Nevertheless, even defects of this nature can cause problems if the tires are retreated without proper treatment being given to correct the defects.
In an attempt to solve some of the problems inherent in visual inspection, other types of testing have been devised. One such method involves over inflating the tire to a degree and either immersing the tire in a fluid or applying a fluid to the outer surface thereof. A leak of air through an orifice or fisher can be detected visually more readily by the observation of a bubbling effect which will occur at the location of the defect.
Non-visual systems have come into use in order to augment visual inspection. Ultrasonic systems have, in recent years, become used more frequently for aiding in the detection of defects as previously discussed.
Although the use of fluids to facilitate detection of defects and systems such as ultrasonic systems have made detection searches more reliable, many problems yet exist. Where many tires are processed, it is important to conduct an inspection as expeditiously as possible. Inspections conducted even with the use of fluids and ultrasonic detectors have done little to accomplish more expeditious processing during inspection.
Recently, a system wherein the tread portion of a tire is sandwiched between a pair of electrodes across which a high voltage electrical potential is generated has been discovered. With this system, if objects such as nails are embedded in the tread portion of the tire or if defects such as orifices or fissures exist, the voltage applied across the electrodes will cause arcing at the point of foreign object or defect. In one such system of which applicant is aware, a tire is mounted for rotation with the circumferential tread portion passing between the electrodes. The apparatus by which the invention is practiced includes an electronics package whereby as a defect is detected by arcing across the electrodes, rotation of the tire will be stopped. Pinpointing the location of the defect is, thereby, facilitated. The location of the defect can be indicated on the surface of the tire, and the tire can be subsequently repaired prior to performing retreading operations. Tires can, thereby, be processed relatively quickly and reliably.
Existing structures by which this high voltage testing procedure is accomplished do, however, in some respects, limit the speed at which tires can be processed. Typically, the construction of a tire is such that the beads (or radially innermost edges of the sidewalls) are spaced axially from each other a smaller distance than are the greater portions of the sidewalls. Consequently, insertion of an electrode into engagement with the underside of the tread portion of the tire requires the prying apart of the beads in order to allow entry of an electrode which has a dimension in a direction axially with respect to the tire, as great as the width of the tread portion thereof. An electrode so dimensioned is desirable in order to maximize the area of the tread portion which is actually tested.
In consequence of this need to pry the beads open to a degree, delays can be encountered. Particularly, in enterprises conducting large scale retreading operations involving large numbers of tires, the total time delay involved on a daily basis can be rather significant.
The invention of the present application is an electrode uniquely configured in order to minimize the time involved in testing any one particular tire unit. It is an electrode specifically designed for use in a system as described above wherein the tread portion of a tire is passed between two electrodes across which a high voltage potential exists. The electrode is configured so that no time need be expended in prying the beads apart in order to facilitate entry of the electrode into the annular cavity within the tire and into engagement with the underside of the tread portion thereof.